Introduction to C++ Programming

Introduction to C++ Programming

Engr. Muniba DCSE UET Peshawar

Contents of Week 02

Data types, Constants

Floating Point Constants, Size, Memory Concepts

Names, Keywords, Identifiers

Declaration and Definition of Variables

A Simple Program: Printing a Line of Text

Another Simple Program: Adding Two Integers

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Introduction to C++ Programming

C++ language

Facilitates structured and disciplined approach to computer program design

Following several examples

Illustrate many important features of C++

Each analyzed one statement at a time

Structured programming

Object-oriented programming

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A Simple C++ Example // C++ simple example #include //for C++ Input and Output int main () { int number3; std::cout > number3; int number2, sum; std::cout > number2; sum = number2 + number3; std::cout

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Important Parts of a C++ program

Comments: //, /* . */

Preprocessor directives : #include

Function main Body of the function

Return statement

Other statements

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Comments

A comment is descriptive text used to help a reader of the program understand its content.

Explain programs to other programmers Improve program readability

Ignored by compiler Single-line comment

Begin with // Example

//allows program to output data to the screen.

Multi-line comment Start with /* End with */ Also called comment delimiter

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Preprocessor Directives

Preprocessor directives

Processed by preprocessor before compiling

Begin with #

Example

#include

Tells preprocessor to include the input/output stream header file

White spaces

Blank lines, space characters and tabs

Delimiter, used to make programs easier to read

Extra spaces are ignored by the compiler

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Function main

A part of every C++ program

Exactly one function in a program must be main

main is a Keyword.

Keyword : A word in code that is reserved by C++ for a specific use.

Header of function main : int main( )

Body is delimited by braces ({ })

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Statements

Instruct the program to perform an action

All statements end with a semicolon (;)

Examples :

return 0;

std::cout

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return Statement

Because function main() returns an integer value, there must be a statement that indicates what this value is.

The statement return 0 ; indicates that main() returns a value of zero to the

operating system. The value 0 indicates the program terminated successfully greater than 0 means an error maybe a different number for a different error if declare our function as int and don't use return will get a

warning from the compiler

One of several means to exit a function Used at the end of main

Namespaces

Namespace: a generalization of scope.

C++ allows access to multiple namespaces with the ' :: ' operator

A namespace lets us distinguish between two names from different places

In C++ the standard library is in the std namespace

Things in no namespace are said to be in the Global Namespace

How to use a namespace

std::cout

What about

Very similar to

Also declares cin, cout and endl

In the global namespace not in the std namespace

This is for compatibility with older versions of C++

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Output Statement (1)

std::cout

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Output Statement (2)

Escape character : backslash : "\"

Escape sequence : A character preceded by backslash (\)

Indicates special character output

Examples :

"\n" Newline. Cursor moves to beginning of next line on the screen

\t Horizontal tab. Move the screen cursor to the next tab stop.

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Good Programming Practices

Add comments Every program should begin with a comment that

describes the purpose of the program, author, date and time.

Use good indentation Indent the entire body of each function one level

within the braces that delimit the body of the function. This makes a programs functional structure stand out and helps make the program easier to read.

2003 Prentice Hall, Inc. All rights reserved.

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1 // Fig. 1.2: fig01_02.cpp

2 // A first program in C++.

3 #include // Preprocessor Directive

4

5 // function main begins program execution

6 int main()

7 {

8 std::cout

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A Simple Program: Printing a Line of Text

Escape Sequence Description

\n Newline. Position the screen cursor to the

beginning of the next line.

\t Horizontal tab. Move the screen cursor to the next tab stop.

\r Carriage return. Position the screen cursor to the

beginning of the current line; do not advance to the next line.

\a Alert. Sound the system bell.

\\ Backslash. Used to print a backslash character.

\" Double quote. Used to print a double quote character.


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1 // Fig. 1.4: fig01_04.cpp

2 // Printing a line with multiple statements.

3 #include

4


6 int main()

7 {

8 std::cout


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1 // Fig. 1.5: fig01_05.cpp

2 // Printing multiple lines with a single statement

3 #include

4


6 int main()

7 {

8 std::cout

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Input stream object

std::cin from Usually connected to keyboard Stream extraction operator >>

Waits for user to input value, press Enter (Return) key Stores value in variable to right of operator

Converts value to variable data type

Example int number1; std::cin >> number1;

Reads an integer typed at the keyboard Stores the integer in variable number1


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1 // Fig. 1.6: fig01_06.cpp

2 // Addition program.

3 #include

4


6 int main()

7 {

8 int integer1; // first number to be input by user

9 int integer2; // second number to be input by user

10 int sum; // variable in which sum will be stored

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12 std::cout > integer1; // read an integer

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15 std::cout > integer2; // read an integer

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18 sum = integer1 + integer2; // assign result to sum

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20 std::cout

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Memory Concepts

Variable names

Correspond to actual locations in computer's memory

Every variable has name, type, size and value

When new value placed into variable, overwrites old value

Writing to memory is destructive

Reading variables from memory nondestructive

Example

sum = number1 + number2;

Value of sum is overwritten

Values of number1 and number2 remain intact

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Fig.1| Memory location showing the name and value of

variable number1.

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Fig. 2| Memory locations after storing values for

number1 and number2.

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Fig. 3 | Memory locations after calculating and storing

the sum of number1 and number2.

age.cpp

#include

using namespace std;

int main()

{

int age=26;

cout

Statements

Instructions

Finish with a ;

(semicolon)

#include


int main()

{

int age=26;

cout

Statement Block

List of instructions

Everything between { and }

(curly brackets, braces)

#include


int main()

{

int age=26;

cout

Functions One of the building block of the C++ program.

#include


int main()

{

int age=26;

cout

Data Types

int, float, void, unsigned int, long, double, char

string, list,

Ways to represent information

#include


int main()

{

int age=26;

cout

Data Type: Char

Size : Single byte

Range: -128 : 127

Hold one character such as a or A

Variable declaration: char ch;

ch = a; // stores a character value a

Data Type: int

Size: 2 bytes

Range: -32768 : 32767

Holds the integer value specified in the range

Type long or long int

Size: 4 bytes

Range: -2,147,483,648 : 2,147,483,647

Data Type: float

Size: 4 bytes

Range: 10e-38 : 10e38 with 6 digits of precision

Holds the numbers that have fractional part e.g., 12.55

Data Type: double

Size: 8 bytes

Range: 10e308 : 10e-308

Holds floating point numbers with 15 digits of precision

Type: long double

Range: 10e-4932 : 10e4932

void datatype

Special data type to represent nothing or an unknown type of data

int main(void)

main function expects nothing

Exactly the same as int main()

void main()

main function returns nothing

In C++ main() should always return an int

Keywords

Sometimes called reserved words.

Are defined as a part of the C++ language.

Reserved for specific purpose

Have special meaning and is known by compiler

Can not be used for anything else!

Examples:

char, int, float, void, signed, if, while, case, else

class, public, friend, this, operator, new, true

Keywords

#include


int main()

{

int age=26;

cout

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Keywords

Cannot be used as identifiers or variable names

C++ Keywords

Keywords common to the C and C++ programming languages

auto break case char const

continue default do double else

enum extern float for goto

if int long register return

short signed sizeof static struct

switch typedef union unsigned void

volatile while

C++ only keywords

asm bool catch class const_cast

delete dynamic_cast explicit false friend

inline mutable namespace new operator

private protected public reinterpret_cast

static_cast template this throw true

try typeid typename using virtual

wchar_t

Constants

Constant is a fixed value that does not change during the execution of the program.

Divided into two types

Numeric Constants

Non-Numeric Constants

Numeric Constants

Numbers are referred to as Numeric Constants Consists of

Numeric digits 0-9 Plus (+) or Minus (-) sign If no sign by-default it is assumed to be positive Decimal point No commas or blanks are allowed

Examples 30 -500 3.14159 0.25432 +100

Numeric Constants

Represented in three ways

Integer constant

Floating-point constant

Exponential real constant

Integer Constant

The numeric constant that doesnt contain a decimal point

Can be positive or negative

Examples 70

+134

0

-500

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Floating-Point Constants

The numeric constants that does contain the decimal point

Can be either positive or negative

Examples

0.3

-56.34

0.008976

Exponential Real Constants

Floating point constant in the E-notation form. Widely used in scientific & engineering

applications. Used to represent very small or very large

numbers Examples

1.23E+2 1.0E3 8.8E-6 3.33E-2

Non-Numeric Constants

Used for non-numeric purposes

To produce output reports, headings, or printing messages

Divided into two types

Character Constants

String Constants

Character Constants

Singular!

One character defined character set.

Surrounded on the single quotation mark.

All the alphabetic, numeric and special characters can be

character constants except backslash and the single quotation

mark.

Examples:

A

a

$

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\\ for backslash

\ for single quote

String Constants

A sequence characters surrounded by double

quotation marks.

Considered a single item.

Examples:

UMBC

I like ice cream.

123

CAR

car

Names

Sometimes called identifiers.

Words that are not reserved.

User defined words or the programmer supplied

names

Can be of any length, but on the first 31 are

significant (too long is as bad as too short).

Are case sensitive:

abc is different from ABC

Must begin with a letter and the rest can be

letters, digits, and underscores.

Identifiers

Variable names and object names

age, height, i, j, x, y, cout

Also function names

main

#include


int main()

{

int age=26;

cout

Variables

Specific storage location in memory where value can be stored

A value, which may vary during program execution.

A variable is the name used to represent a piece of information.

Declaration & Definition of Variables

All the variables must defined and declared before usage.

Declaration introduces a variables name into a program

If the declaration also set aside memory for the variables it is called the definition

Variables can be assigned a value at the time of declaration

Declaration statements

int age;

string user_name;

float height, weight;

int age=26;

string user_name="Matt";

float height=1.75, weight=122.5;

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Algorithms

Computing problems

Solved by executing a series of actions in a specific order

Algorithm a procedure determining

Actions to be executed

Order to be executed

Example: recipe

Program control

Specifies the order in which statements are executed

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Pseudocode

Pseudocode

Artificial, informal language used to develop algorithms

Similar to everyday English

Not executed on computers

Used to think out program before coding

Easy to convert into C++ program

Only executable statements

No need to declare variables

Introduction to C++ Programming

Documents

main main

c program comments

namespace std

c programming c language

simple program

c input

output int main

header of function main